It is well-known that a wireless link can be created between mobile personal communication apparatus such as a mobile telephone handset and a remote unit such as a headset, using a wireless link. Commonly, the wireless link is established according to the well-known Bluetooth specifications described in detail at www.bluetooth.org. Briefly, Bluetooth makes use of an encrypted 2.45 GHz channel hopping radio link, which may provide duplex communication between local devices. Each device is provided with a unique identification code which is communicated to the other device in a process known as pairing so that a secure wireless link can be established between them. The devices are usually arranged in a master and slave relationship and the master device may continually seek to establish communication with the slave.
Other wireless links are known, for example infrared and also Zigbee developed by the Zigbee Alliance, described at www.Zigbee.org.
A problem with these known arrangements is that the personal mobile communications apparatus and the remote unit are generally battery powered and in order to provide automatic wireless connection between the devices, the circuitry associated with the wireless link needs to be continually on. However, the headset may not necessarily be configured ready for use. For example, the headset may be switched off or not deployed on the head of a user. Also, the circuitry for the wireless link in the handset may be switched off, so that when the headset is deployed by a user, it may not be possible to establish an automatic wireless connection from the headset to the handset.
Also, some users of handsets prefer to leave the wireless link circuitry switched off to avoid third parties forming an unwanted connection to the handset, which might permit data to be extracted from the memory of the handset. This is known as “bluesnarfing” in relation to Bluetooth.
Another problem that can arise is that when a wireless link is established between the handset and the headset, the handset adopts a profile by which communication for a telephone call through the mobile telephone network is routed solely through the wireless link between the handset and the headset. For an incoming call, an alerting signal is sent through the wireless link to the headset but not necessarily to the loudspeaker of the handset, on the assumption that the headset is in the vicinity of the user's ear. However, if the headset is not actually in place at the user's ear but instead worn around the neck or otherwise in close vicinity of the user, they will not be able to hear the alerting signal for the incoming call. Hitherto, to avoid this problem, the profile adopted by the telephone handset, may be defined so that both the loudspeaker of the telephone handset and the headset produce an audible alerting signal when the call is routed to the headset. However, the loud, audible alerting signal from the handset can be a problem when the user is wearing the headset to avoid disturbing other people.
Alternative approaches to providing a connection between devices situated about a person have been proposed that make use of the person's body as a conduit for electrical signals. U.S. Pat. No. 6,754,472 to Williams et al discloses an arrangement by which individual devices are connected in a network by means of electrodes that provide electrical connections to the human body.
WO2003/100739 to Ident Technology AG discloses a system in which objects in the vicinity of the human body are detected by sending electrical signals through the human body, the signals being created through the use of an electrode that capacitively couples an electrical signal to the human body.